Abseiling is a technique used to descend steep surfaces such as cliff faces and is often used by persons involved in activities such as mountain climbing, canyoning and caving. In order to abseil down a cliff face, one end of a rope is made fast at the top of the cliff and the person making the descent then slides down the rope, The rope is passed either around the body of the person or more usually through a descender attached to a harness worn by the person such that the passage of the rope around the body or through the descender provides sufficient friction to slow the rate of descent to a safe speed,
A descender comprises rope engaging surfaces around and between which the rope travels, along a tortuous path, to provide frictional engagement between the rope and the descender, The rate of descent is normally controlled by holding the free or tail end of the rope to control the tension on the rope where it emerges from the descender and thereby to control the degree of frictional engagement between the rope and the descender which in turn controls the rate of descent,
Descenders used in abseiling vary greatly in performance and complexity, there being a variety of relatively simple devices which rely on frictional engagement between the rope and metal rings or racks about which the rope is wrapped, and a number of more complex descenders which incorporate a braking mechanism which allows the friction between the rope and the descender to be varied other than by simply controlling the free or tail end of the rope, The earliest of these more complex devices had a handle or lever which when operated tended to increase the friction between the descender and the rope. This type of descender was not a great improvement over the more simple devices as the brake was not self-engaging and therefore, if the user was knocked unconscious, he would fall in the same way as the user of the earlier devices.
The present invention is derived from a class of descenders wherein the variable braking action of the descender increases when the handle is released. Usually, the force required to initiate the braking action is provided by the frictional engagement of the descender with the rope travelling therethrough. It is also possible to have arrangements which are operated by springs. Spring operated arrangements have the disadvantage that the restoring force of the spring may reduce with age or the spring may become damaged without this being noticed by the user, thereby decreasing the effectiveness of the descender.
An improved type of descender was disclosed in U.S. Pat. No. 4,596,314 to the present applicant which provides a descender having a simplicity of construction and operation which was not achieved by earlier prior art descenders. The disclosure of this United States patent is incorporated herein by reference.
A disadvantage of the descender disclosed in U.S. Pat. No. 4,596,314 is that the actuation and release of the self-engaging brake can in some situations be rather abrupt or jerky. For example, it can be difficult for inexperienced users to smoothly control the braking action.
The first embodiment of the present invention is intended to provide a modification to the descender shown in U.S. Pat. No. 4,596,314 which allows the user to smoothly control the braking action and thereby avoid or minimize the Jerkiness which can be experienced with the use of this known type of descender.
Another problem with the descender disclosed in U.S. Pat. No. 4,596,314 is that, when used with a large diameter rope, too much resistance may exist between the rope and the descender as the rope moves along the tortuous path around the two spaced sheaves. The second embodiment of the present invention provides a means of solving or alleviating this problem.